NEW YORK (Reuters Health) - Teens were more likely to diet and use other unhealthy measures to control their weight when their parents talked to them about losing weight or the importance of being thin, in a new study.

Conversely, family conversations about healthy eating that did not involve the topic of weight were linked to fewer unhealthy behaviors, such as laxative use and skipping meals - especially among heavier adolescents.

"It's important to (have) conversations that focus on healthy eating as a cause for healthy bodies and strong bones, rather than a cause for weight and size," said Jerica Berge, who led the new study at the University of Minnesota Medical School in Minneapolis.

Past studies have shown that being told to diet or being teased about weight by a parent is harmful to children, she said. But that still leaves the question of what families who genuinely want to help an overweight child should be talking about.

She and her colleagues surveyed 2,800 racially and socioeconomically diverse middle and high school students and one or both of their parents about food, weight and related conversations.

Twenty-eight percent of mothers of normal-weight teens said they'd talked about healthy eating with their child, and 33 percent said they'd had conversations about weight or the need to lose weight.

That compared to 15 percent of mothers who talked solely about healthy eating with their overweight teens and 60 percent who discussed losing weight. Rates were similar for conversations initiated by fathers.

The researchers found that dieting and unhealthy eating patterns were more common among both normal weight and overweight children of parents who focused on weight.

For example, 64 percent of overweight teens whose mothers talked about weight and weight loss had used worrisome weight-control behaviors. That compared to 41 percent when family discussions were only about healthy eating and 53 percent when mothers didn't discuss food or weight at all.

Likewise, 39 percent of normal weight children whose mothers brought up weight had used unhealthy behaviors, compared to 30 percent of those with mothers who emphasized being healthy, Berge's team reported Monday in JAMA Pediatrics.

"If a child is concerned about their weight and they want to talk about their weight, you want to have an open conversation with them," said Alison Field, who studies weight and unhealthy eating at Boston Children's Hospital but wasn't involved in the new research.

However to have that talk with a kid who doesn't really want to discuss weight probably won't be helpful, she told Reuters Health.

Because the surveys represent a single point in time, Berge and her colleagues couldn't determine whether family conversations or a teen's dieting and unhealthy weight-control behaviors came first.

Field said future studies will ideally follow teens who don't engage in any unhealthy weight-related behaviors to see how family talks about food affect who does and doesn't start.

Still, the researchers said, the findings suggest parents should stay away from conversations that focus on losing weight and being thin - and talk about the general importance of healthy eating instead.

"Healthy eating conversations are not going to be harmful, and they may be helpful," Field said.

"That to me is a positive message for parents who have an overweight kid and are struggling because they don't know what to do," Berge added.